Hack and crack proof SSH on Linux

ItÃ¢â¬â¢s inevitable: if your computer is Internet-connected you will have people coming a-knockinÃ¢â¬â¢. Fortunately Linux users are more savvy than to think any keep-alive ping or other piece of Internet flotsam is a hack attempt. Even so, itÃ¢â¬â¢s simply a matter of time before your routerÃ¢â¬â¢s lights flash heavily and /var/log/auth.log (/var/log/secure on RedHat) fills with chilling messages like these: